Optimization of sulphur content in LiMn2O4−ySyLiMn_2O_{4-y}S_y spinels as cathode materials for lithium-ion batteries

Sulphur doped lithium manganese spinels with a nominal composition of LiMn2O4-ySy (0≤y≤0.02) were synthesized by a modified sol-gel method followed by calcinations at 300 and 650 °C in air. The prepared materials were characterized in terms of physicochemical properties using X-ray powder diffraction (XRD), differential scanning calorimetry (DSC) and electrical conductivity studies (EC). Electrochemical characteristic of Li/Li+/LiMn2O4-ySy cells was examined by galvanostatic charge/discharge tests (CELL TEST), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It was shown that small amount of sulphur in LiMn2O4 spinel enhances the structural integrity of the host material and increases the electrochemical performance

Novel method of preparation of C/Sn−SnO2C/Sn-SnO_2 nanocomposite Li-ion anode material derived from plant polysaccharides

C/Sn - SnO 2 nanocomposite was obtained in one step pyrolysis and carbore duction process, providing formation of tin - based nanograins encapsulated in carbon buffer matrix derived from plan t polysaccharide (potato starch). Electrical conductivity of t he obtained material was carried out within temperature range - 20÷ 40 ̊ C. Cyclic voltammetry (CV) and charge - discharge tests were pe rformed in Li/Li + /(C/Sn - SnO 2 ) R2032 - type coin cells within 0.02 ÷ 1 .5 V potential range. Furthermore , electrochemical impedance spectroscopy (EIS) was used to characterize electrochemica l properties of the nanocomposite. The C/Sn - SnO 2 anode material provided at least 538 mAh g -1 at C/20 – rate and revealed good coulombic efficiency and capacity retention in charge - discharge cell tests

A novel concept for the synthesis of nanometric LiFePO4LiFePO_4 by co-precipitation method in an anhydrous environment

LiFePO 4 with high purity and good crystallinity was prepared by an improved environmentally benign and low - cost co - precipitation method. The precipitate was synthesized at a room temperature using technical grade reagents on ethylene glycol as a medium . LiFePO 4 precursor was characterized by TGA/DTG measurement and 650 ◦ C was found to be the optimal calcination temperature . The obtained Li F ePO 4 was characterized by X- ray diffraction (XRD), Transmission Electronic Microscopy (TEM), and nitrogen adsorption/desorption measurements ( N 2 - BET). The X- ray diffraction studies confirmed formation pure phase of orthorhombic LiFePO 4 ( Pnma space group) without any impurities. The developed co - precipitation method in an anhydrous environment is environmental friendly, cheap and can be easily scalabl

Morphology and electrical conductivity of carbon nanocoatings prepared from pyrolysed polymers

Conductive carbon nanocoatings (conductive carbon layers-CCL) were formed on \alpha-Al_{2}O_{3} model support using three different polymer precursors and deposition methods. This was done in an effort to improve electrical conductivity of the material through creating the appropriate morphology of the carbon layers. The best electrical properties were obtained with use of a precursor that consisted of poly-N-vinylformamide modified with pyromellitic acid (PMA). We demonstrate that these properties originate from a specific morphology of this layer that showed nanopores (3-4 nm) capable of assuring easy pathways for ion transport in real electrode materials. The proposed, water mediated, method of carbon coating of powdered supports combines coating from solution and solid phase and is easy to scale up process. The optimal polymer carbon precursor composition was used to prepare conductive carbon nanocoatings on LiFePO_{4} cathode material. Charge-discharge tests clearly show that C/LiFePO_{4} composites obtained using poly-N-vinylformamide modified with pyromellitic acid exhibit higher rechargeable capacity and longer working time in a battery cell than standard carbon/lithium iron phosphate composites

Pyrolytic carbons derived from water soluble polymers

Conductive pyrolytic carbon materials were obtained in wet impregnation process followed by controlled pyrolysis. Poly- N -vinylformamide (PNVF) as well as mix- ture of PNVF and pyromellitic acid (PMA) were applied as carbon precursors. Composition of carbon precursors was optimized in terms to obtain best electrical properties of pyrolytic carbons. Mixture of PNVF and PMA as well as pure PNVF were deposited on the model alumina ( a -Al 2 O 3 ) support to form conductive carbon layers (CCL). The opti- mal composition of the polymer precursors was determined by Raman spectra and electrical conductivity measurements. The carbonization conditions were optimized using com- plementary thermal analysis methods (EGA(FTIR)–TG/ DTG/STDA). It was found that the addition of PMA to polymer precursor PNVF decreases temperature of forma- tion of condensed graphene structures, domains of electrical conductivity, thus, the formation temperature of pyrolytic carbons with desired electrical properties may be decreased

An influence of thermal treatment conditions of hydrotalcite-like materials on their catalytic activity in the process of N2ON_2O decomposition

Hydrotalcite-like materials containing apart from magnesium and aluminum also copper, cobalt, nickel, and iron were prepared by a co-precipitation method. Thermal transformations of hydrotalcite-like materials were studied by thermal analysis methods as well as XRD, UV-vis-DRS, and XPS measurements of the samples calcined at various temperatures (600, 700, and 800 {\textdegree}C). Calcined hydrotalcites, especially those containing cobalt and copper, were found to be active and selective catalysts of N2O decomposition. It was shown that an increase in the calcination temperature significantly activated the Co-containing catalysts. Promotion of the samples with potassium resulted in activation of the hydrotalcite-based catalysts